NGEZ-1 Venturi

[djh82uk]

Hi Guys

Im having a go at the NGEZ-1 engine to get back into machining, engine wise I have only made two basic steam engines (one being the Hmem EZE).

No I have started on the venturi as I had the right size stock. Im not averse to scrapping a part and having another go at this stage as it's been a while and I had a lot to learn back then when I had to take a break from machining.

So anyway i have a few questions, I have atatched the diagram for the part ( they are paid for plans but have only included the venturi).

The cone part of it, the diagram shows it as 10 degrees on the outside and 20 degrees on the inside. How can I taper the inside of the cone? My cutter is too big to get in there. Although I can set the slide to 20 degrees, do I need to make small cutter?

So far I have a square centre, the small round section (to size) and the cone to size but not the inside. I have also drilled the hole.

Now for the rest Im guessing I just need to square off the square section on the mill and use the Z axis readout to get the correcnt dimensions. But how would you reccomend doing the cross hole? Workholding wise as I have decent vice with parallels but I can only use one as the part is too thin, and so any attempt to drill will hit the parallel which obviosuly I want to avoid.

Lastly I have a 0.125" reamer but only metric drills, should I use a 3mm or 3.1mm drill before reaming? Will the 3mm leave too much material for the reamer to remove?

Thanks

DJH

 

[vcutajar]

DJH

Can I suggest making yourself a D-bit with the proper taper. I made a similar tool when I was machining the inside venturi of the Kiwi carb and it worked a treat in phosphor bronze. In aluminium should be even easier.

Vince

 

[djh82uk]

Thank you Vince that is great, I will look into how to make a D-bit and see how I get on

Thanks

DJH

 

[djh82uk]

Ok, so to confirm, I need to buy some 1/4" silver steel, cut the taper to 20 degrees on the lathe, mill, or grind half of the taper off into a cross-section, harden & temper it and then run along an oil stone?



Thanks

DJH

 

[vcutajar]

Yes that should be correct. As you are working in aluminium you can get away with it by just hardening it.

There has been a recent discussion lately:

http://www.homemodelenginemachinist.com/f26/d-bit-question-19785/

Have a look at reply number 7.

 

[djh82uk]

Well I have ordered the silver steel to make the d-bit, tody i received the stock for the crankcase. How should I attack this? (picture atatched)

My plan was to mount it in the four-jaw (which i hate as trying to get it centered is a pain as if the surface is not at the same angle as it's opposite when tested with a dti it messes up my readings), turn the round section (would I need a LH and RH cutter to do the two shoulders?)

Sharpen up a parting cutter for the fins, bore the main cylinder and square up the sides on the mill.

But how the hell do I cut the hole at 90 degrees to the cylinder bore? The plans say it has to be perfectly 90 degrees. Is a faceplate the only way (as I don't have one ). And would'nt that also be a real pain to line up?

Would I have to scribe the center for the hole and line that up with the tailstock by eye?

Thanks

DJH

 

[vcutajar]

I am assuming that the picture is the final product and that the material is aluminium.

At first glance this is how I might go about it.

Mill the material to the final square dimension. Mark the position of the fins and the central round section. Put it in the 4 jaw chuck and indicate it accurately. Drill and ream (or bore) the cylinder. Make the fins with the grooving or parting tool. With the same tool I would try and machine the central section. Watch out for tool deflection.

Now put it in the mill vice and drill and ream (or bore) the lower hole.

That would be my plan of action but usually these plans change as work progresses.

Vince

 

[djh82uk]

Thanks Vince

Yes that is the finished item, and it is made from aluminium. Your method sounds a lot less backwards

I need to get better at holding square objects in the 4-jaw. Also need to get a boring head for the mill, I guess it's drill/ream for now. Do you think a normal parting tool would be ok for the central round section? or is there a better cutter design I could grind to reduce chatter etc?

Thanks

DJH

 

[kf2qd]

A parting tool would do just fine. Either that or do some grinding on a HSS blank and make a blade type tool to cut the grooves and the cylindrical section.

In the hobby side of things you sometimes have to be a bit creative with how you approach a part. Sometimes you have to use a slower proces because you lack the machine or tooling to do it the easy/correct way.

A tool you might make for centering to a punch or scribe mark is a pump center. It is basically a 2 piece pin with a center hole in one end, a point on the other and a spring in the middle to work against. You put the point in the center of the scribe marks and the other end in your tailstock center and your indicator against the side of your pump center. You can start out with the indicator nearer the tailstock when you start ans as the piece in the 4-jaw is closer to center you can move the indicatro closer to the workpiece. Or you can learn to pull the indicator in and out by hand and center the square part. When you are centering a long square part you mount the indcator off the carriage and then move the cariage side to side whi;e indicating the long axis of the part to make sure it is square in the chick.

Take time to look over the process you want to do. If you do it differently than others it might be because you don't have the same tools they have. No problem. There are more that one way to skin a cat. Just do your best to do it safely. SLow down a bit and do it safely. Scars are not a sign of valor, they are a reminder to to not be so stupid next time. (Yes, I have a few stupid marks...)

 

[jack620]

There are a couple of good vids on YouTube showing the method described above for truing square stock in the 4 jaw.

I recently made a pump centre for centring to a punch mark. It works beautifully. I used it to centre the crankcase for my ML Midge in the 4 jaw.

 

[djh82uk]

Thanks guys, will have a look on youtube at the mentioned process, and have a go at grinding a cutter to to be the right width for the fins.

Thanks

DJH

 

[djh82uk]

Hi Guys

quick few questions, I have finished the carb and cylinder head, and done as much as I can on the cylinder, the vertical bore is done, but for the horizontal bore what would be the best method? I guess i have 3 options:

Buy drills upto 14mm and make a D-bit as a reamer

Buy a Boring head for the mill (I want to get one at some point anyway, but need to save up)

Buy a faceplate for the lathe and a clamping set but worried about centering without extra cost

What do you think?


Also I have started the crankcase but a bit stuck on how to the radiused cutout, do i mount it vertically (im guessing horizantally) or horizontally in the mill vice and use a ball nosed cutter? And then to use the rotary table to do the rounded section?

Pics atatched